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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
2011,2012 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS/RT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
---
A special exception to the GPL can be applied should you wish to distribute
a combined work that includes ChibiOS/RT, without being obliged to provide
the source code for any proprietary components. See the file exception.txt
for full details of how and when the exception can be applied.
*/
/**
* @defgroup PWM PWM Driver
* @brief Generic PWM Driver.
* @details This module implements a generic PWM (Pulse Width Modulation)
* driver.
* @pre In order to use the PWM driver the @p HAL_USE_PWM option
* must be enabled in @p halconf.h.
*
* @section pwm_1 Driver State Machine
* The driver implements a state machine internally, not all the driver
* functionalities can be used in any moment, any transition not explicitly
* shown in the following diagram has to be considered an error and shall
* be captured by an assertion (if enabled).
* @dot
digraph example {
rankdir="LR";
node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.9", height="0.9"];
edge [fontname=Helvetica, fontsize=8];
uninit [label="PWM_UNINIT", style="bold"];
stop [label="PWM_STOP\nLow Power"];
ready [label="PWM_READY\nClock Enabled"];
uninit -> stop [label="pwmInit()"];
stop -> stop [label="pwmStop()"];
stop -> ready [label="pwmStart()"];
ready -> stop [label="pwmStop()"];
ready -> ready [label="pwmEnableChannel()\npwmDisableChannel()"];
}
* @enddot
*
* @section pwm_2 PWM Operations.
* This driver abstracts a generic PWM timer composed of:
* - A clock prescaler.
* - A main up counter.
* - A comparator register that resets the main counter to zero when the limit
* is reached. An optional callback can be generated when this happens.
* - An array of @p PWM_CHANNELS PWM channels, each channel has an output,
* a comparator and is able to invoke an optional callback when a comparator
* match with the main counter happens.
* .
* A PWM channel output can be in two different states:
* - <b>IDLE</b>, when the channel is disabled or after a match occurred.
* - <b>ACTIVE</b>, when the channel is enabled and a match didn't occur yet
* in the current PWM cycle.
* .
* Note that the two states can be associated to both logical zero or one in
* the @p PWMChannelConfig structure.
*
* @ingroup IO
*/
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